/Engine/Source/Runtime/MeshDescription/Public/MeshDescriptionBase.h
Adds a new polygon to the mesh with the given ID. This will also make any missing edges, and all constituent triangles.
void CreatePolygonWithID ( [FPolygonID](API\Runtime\MeshDescription\FPolygonID) PolygonID, [FPolygonGroupID](API\Runtime\MeshDescription\FPolygonGroupID) PolygonGroupID, [TArray](API\Runtime\Core\Containers\TArray)< [FVertexInstanceID](API\Runtime\MeshDescription\FVertexInstanceID) > & VertexInstanceIDs, [TArray](API\Runtime\Core\Containers\TArray)< [FEdgeID](API\Runtime\MeshDescription\FEdgeID) > & NewEdgeIDs )